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Modular synths have recently piqued my interest, but patch cords are hell. I have been thinking of some intelligent way to route signals - something microcontroller-driven and remembering different presets. I came across analog crosspoint switches - they are used to switch high-frequency signal, television and the like, and have 16 inputs and 16 outputs. They, however have unnecessarily high bandwidths (60+MHz) and prices ($30+/chip) for this.

I'm looking for a 16x16 switch (or a good way to implement one), suitable for modular synth use, and not having dedicated inputs and outputs - just 16 points which can be freely connected to one another.

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Uso 4066 analog switches. These make perfectly good audio analog switches (See This) and have been used even in high-end audio (my old Quad 44 preamp uses similarily specced chips). These have been around for a long time and there may be better moderen equivelents. You would need a good few to build up a large matrix but they are easy to drive from ttl/cmos, 5v/3.3v etc.

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  • \$\begingroup\$ The datasheet says Vin: 0 V to Vdd, so you need to clamp the audio signal to some voltage in the middle. \$\endgroup\$
    – AndreKR
    Commented Mar 4, 2011 at 10:06
  • \$\begingroup\$ @AndreKR, you could also run the 4066 from a dual supply to ensure that the signal is between the two power rails, but you'd have to shift the levels of the control inputs as well. \$\endgroup\$
    – Theran
    Commented Mar 5, 2011 at 8:49
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I afraid you might not find any cheaper things. It's basically a matrix of 16x16 FET's with control logic. Even in it's simplest implementation it have good bandwidth, so 60Mhz is a basic one :-)

You may be lucky to build that from discreete components (256 FET + 32 shift registers) - but it will probably cost the same.

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  • \$\begingroup\$ Thanks. Indeed the general bandwidths were in the range of 300MHz, and the prices often topped $100, the one I mentioned was the cheapest one I found in Analog Devices' catalog. Anyway, thinking of a discrete solution, I could probably implement it on a double-sided PCB, and I would probably only need about 120 FETs for a 16 x 16 matrix - but what kind? Wouldn't JFETs color the sound? \$\endgroup\$
    – avramov
    Commented Feb 21, 2011 at 14:56
  • \$\begingroup\$ I don't like JFETs :-) There are 4-wire FET's - they might be more appropriate. It's all depends on price. Also, as guys suggest - there are 8->1 analog multiplexors for about 0.2$, so you can build what you need from them. \$\endgroup\$
    – BarsMonster
    Commented Feb 21, 2011 at 17:16
  • \$\begingroup\$ I know those mux chips - some quad CMOS switches would be more up my alley. And those 4-wire FET's, maybe you could give me a part/model number to look up? (: \$\endgroup\$
    – avramov
    Commented Feb 22, 2011 at 12:23
  • \$\begingroup\$ Havan't quickly found any modern ones, I've seen only 'made in USSR' in such form. 4rth pin is connected to 'body' so that you can make sure that diode does not conduct. \$\endgroup\$
    – BarsMonster
    Commented Feb 22, 2011 at 14:46
  • \$\begingroup\$ TEA6422 is a chip designed for audio switching. \$\endgroup\$
    – AndreKR
    Commented Mar 4, 2011 at 10:09

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